The present disclosure relates to optical scanning devices and image forming apparatuses including an optical scanning device.
As image forming apparatuses, such as copiers, printers, etc. an image forming apparatus employing an electrographic process has been known. The electrographic image forming apparatus includes an optical scanning device and a developing device. The optical scanning device emits light for formation of an electrostatic latent image on a photoreceptor. The developing device develops the electrostatic latent image formed on the photoreceptor to make it a toner image.
The optical scanning device includes a casing to accommodate a polygon mirror, an imaging lens, etc. A light emitting port is formed in the casing to emit light. The light emitting port is blocked with a covering. The covering may be made from transparent glass covering, for example.
Incidentally, the surface of the glass covering may contaminate with toner and the like, or dust or the like may adhere to the surface of the glass covering. When so, the optical characteristics of the optical scanning device may degrade. Degradation of the optical characteristics may cause an image defect. In view of this, the optical scanning device is generally provided with a cleaning mechanism to periodically clean the surface of the glass covering.
A typical cleaning mechanism may include a screw shaft, a holding member, and a cleaning member. The screw shaft is arranged along the glass covering. The holding member is screw inserted in the screw shaft. The cleaning member is held by the holding member. A protrusion is formed on the inner peripheral surface of the holding member to engage with a screw groove of the screw shaft. Positive or reverse rotation of the screw shaft causes the cleaning member to reciprocate together with the holding member along the glass covering. Reciprocation of the cleaning member in this manner can clean the surface of the glass covering.
In order to appropriately control the movement of the cleaning member, a sensor may be provided to detect the position of the cleaning member. However, provision of the sensor may increase the cost. For this reason, a predetermined time period is set usually for movement of the cleaning member. When the predetermined movement time elapses, the moving direction of the cleaning member is reversed. In order not to leave a non-cleaned region of the glass covering, the movement time of the cleaning member is set longer usually.
Further, springs are provided on the opposite ends of the holding member of the cleaning mechanism in the axial direction of the screw shaft. When the movement direction of the cleaning member is changed by reverse rotation of the screw shaft, the compression force of one of the springs pushes back the holding member to allow the protrusion of the holding member to engage with the screw groove of the screw shaft.